Electron tube stem having break-away leads



Aug. 17, 1965 w. K. BATZLE ELECTRON TUBE STEM HAVING BREAK-AWAY LEADS Filed Sept. 12, 1962 INVENTOR. mil/4114K 54721.6-

United States Patent 3,201,509 ELuornoN runs sraM HAVING BREAK-AWAY LEADS William K. Batzle, Bloomfield, N.J., assignor to Radio Corporation of America, a corporation of Delaware Filed Sept. 12,, 1962, Ser. No. 223,179 2 '(Ilairns. (Cl. H t-50! 1) This invention relates to electron discharge devices and particularly to the electrode supporting stems of such devices.

In certain types of electron discharge devices such as oetal electron tubes, an envelope is provided including a stem member which comprises a flat disk-like wafer through which a number of conductors extend in sealed vacuum tight relationship. Within the tube, the conductors support and make electrical contact with the tube electrodes. Without the tube, the conductors make contact with the circuit components associated with the tube.

In certain ones of such tube types it is desirable, for reasons to be described hereinafter, that some of the stem conductors be dummy conductors, that is, that the conductors extend inwardly from one side of the stem into the tube but not outwardly from the other side thereof. One trouble with this requirement is that in the manufacture of the stems used in these tube types it is desirable, as known, to fabricate the stems with conductors which extend outwardly from both sides of the stern wafer. Hence, in order to provide the dummy conductors, it is the practice to remove the lengths of conductors extending from the external side of the stem wafer.

According to one prior art method for removing the external portions of the stern conductors, the conductors are made of three wires or rods welded end to end. The conductors are disposed relative to the stern water such that the joint between the external end rod and the intermediate rod of smaller diameter is disposed substantially flush with the external surface of the wafer. Exertion of a bending force against the external rod causes the joint to break.

One disadvantage of this prior art method is that it is necessary to position the joint between the two rods almost exactly flush with the surface of the wafer. If the joint is positioned within the wafer, the bending force applied to the external rod results in cracking of the wafer and destruction of the hermetic seal between the wafer and conductor. If the joint is positioned outside the wafer, the bending force will not break the joint as desired, but merely bend a portion of the intermediate rod extending outside the wafer. This is because the intermediate rod, as will be described, is usually made of a soft, flexible material known as Dumet. As known, careful conductor positioning relative to the stem wafer is relatively difficult to achieve using present stem manufacturing methods.

A further disadvantage of the prior art method is that it uses conductors of two or more abutting rods to provide the joint which is positioned flush with the wafer surface. This is undesirable because in some instances, as will be described hereinafter, it is desirable to use a single rod conductor.

A still further disadvantage of the prior art method is that stems having both through and dummy conductors are fabricated using conductors of different sizes. That is, the dummy conductors have long intermediate rod sections in order that the joint between the intermediate and end rods may be disposed flush with the surface of the wafer.

The through conductors have shorter intermediate rod sections to dispose this joint within the wafer. When the conductors of each type become mixed together, as they frequently do when defective stems are discarded, for example, it has been found too expensive to separate the two types of conductors to permit reuse thereof. Hence, the mixed together conductors are simply scraped. If the through and dummy conductors were identical, the conductors could be reused.

It is therefore an object of this invention to provide a stem for electron devices having through and dummy conductors and which overcomes the above-described problems associated with prior art stems.

Another object of this invention is to provide a stem for electron devices having through and dummy conductors wherein external portions of the conductors are broken oif to provide the dummy conductors but wherein the relative positioning of the conductors with respect to the stem wafer is not critical.

Other objects of this invention are to provide stems having through and dummy conductors wherein when an external portion of a conductor is broken away to provide a dummy conductor, the break always occurs closely adjacent and outside the surface of the wafer; wherein the bending force applied to the external portion of the conductor does not crack the wafer or break the conductor to wafer hermetic seal; wherein single rod conductors may be used; and wherein the through conductors may be identical to the conductors to be converted to dummy conductors.

For achieving these objects in accordance with certain embodiments of this invention, an electron discharge device stem is provided which comprises an insulating wafer having conductors extending therethrough in vacuum tight relation. The conductors may be of single or multiple rod construction, and a portion of the conductors adjacent the external surface of the wafer may be provided with one or more areas of reduced resistance to bending forces. .T hat is, for example, a number of notches or grooves or the like may be provided along the conductors starting from a point external to the wafer and extending to a point therein. As will be described hereinafter, upon exertion of a bending force against the externally extending portion of the conductors, the conductors break outside the wafer at the weakened area adjacent the wafer surface. No excessive bending force is applied to the wafer which would tend to crack the wafer, and the conductor is always broken off close to the surface thereof. Further, during manufacture of the header, the conductors need be positioned relative to the wafer only to the extent that the wafer surface is disposed between the ends of the Weakened areas. An advantage of this arrangement is that the dimensional control required over the conductor-wafer relative positioning is significantly less than that required in the manufacture of the prior art stems described.

Other embodiments of the invention and advantages thereof will become clear as the description of the invention proceeds in connection with the drawings wherein:

FIG. 1 is a view in perspective of a stem made according to this invention prior to removal of the external portions of some of the conductors;

FIG. 2 is a view similar to FIG. 1 but with the external portions of some of the conductors removed to provide dummy conductors;

FIG. 3 is an enlarged fragmentary section of the stem shown in FIG. 1 and showing a conductor embedded in a 3 wafer and extending therefrom prior to removal of the external portion of the conductor; and,

FIG. 4 is a view similar to FIG. 3 but showing a modification of the conductor.

In FIG. 1 is shown a stem lid of a type which may be made according to this invention and which has utility in electron tubes of a type known as octal or glass tubes. Stern It comprises a fiat disk-like wafer 12 usually of glass, a plurality of conductors 14 and hermetically sealed through the wafer and extending beyond each side thereof, and an exhaust tubulation 17, Conductors 14 and 15 may be composed of three rods 24, and 26 (FIGS. 3 and 4) butt welded together. The internal rods 24 and the external rods 26 may be composed of alloys of nickel or iron, and intermediate rods 25 made from a copper clad alloy of nickel and steel with an intermediate bonding layer of brass known as Dumet. Durnet, as known, is used because its coefiicient expansion is substantially similar to that of the wafer 12 glass, thereby permitting proper Sealing of the Dumet to the wafer.

Within an electron tube using the stem'lltl, the wafer 12 serves as a header member closing one end of the tube, the internal rods 24 of conductors 14 and 15 serve as'supporting and connecting means for the tube electrodes, and the external rods 2-6 of conductors 14 serve as terminals for the tube electrodes. Exhaust tubulation 17 is used to exhaust the tube after the stern and electrodes mounted thereon are sealed to the tube envelope, the tubulation 17 then being tipped off.

For adding mechanical strength to the tub-e and to facilitate socketing thereof, a plastic or metal base is usually secured about the stem end of the tube. The base is provided with a number of hollow base pins, each of the external rods 26 of conductors 14 being inserted within and electrically secured to a corresponding pin. Prior to the addition of the base to the tube, the external portions or rods 26 of the conductors 15 are removed from the stern (FIG. 2), as will be described. As mentioned, the dummy conductors 15 may provide support for the tube electrodes within the tube envelope but do not extend outwardly therefrom into the tube base. The electrodes supported on the dummy conductors are also secured to through conductors in order to provide external electrical connections with these electrodes. The electrodes thus may be rigidly supported within the tube by several conductors 14 and 15 while the number of conductors 14 extending from the tube is reduced. The number of base pins may be reduced accordingly, thereby reducing the cost of the base, hence that of the tube.

For facilitating removal of the external rods 26 of conductors 15 to provide the dummy conductors, rods 26 i may be provided with a number of spaced apart cut-outs or notches 28 along a length 349 thereof as shown in FIG. 3. Notched length 3t? extends along rod 26 so that a part thereof is embedded within wafer 12 of stem 10 while the remainder of length 30 is external of wafer 12. The joint between rods 25 and 26 is wholly within wafer 12. Wafer 12 may have a thickness, for example of 100 mils, and notched length 3% may be 187 mils long. Rod 26 may have a diameter of mils and notches 28 may have a depth of 7 mils and be spaced 16 notches to the inch. v To remove external rod 26, a sidewise bending force may be applied to the outer end of rod 26. Notches 28 provide areas of weakened resistance to bending moments.

Since the length of the moment arm between the aphermetic seal between the wafer 12 and the conductor is not broken. For concentrating the bending force at a small area to produce sharp breaks, notches 28 are preferably of V-shaped cross-section.

The reason many notches are preferably provided, rather than just one at the surface of water 12, is to simplify fabrication of the stem. During stem fabrication, no single notch need be accurately positioned with respect to wafer. All that is required is that the external surface 32 of wafer 12 be positioned between the ends of length 39. Because of the close spacing between the notches, a notch 28 will always be positioned closely adjacent the external surface 32 of wafer 12. Hence, the break will always occur close to the wafer surface. Provision of only one notch positioned flush with the wafer surface is also within the spirit of this invention. Although requiring careful positioning, such single notched conductors provide certain advantages, as will be described.

FIG. 4 shows another embodiment of the invention. As shown, a continuous thread as, prefer-ably of V-shaped cross section, may be provided in rod 26. Here too, the rod will always break off close to the external surface 32 of the wafer 12 and on the outside thereof. Also, the rod need not be positioned critically with respect to water 12 during stem fabrication. The continuous thread 36 provides a weakened area adjacent wafer surface 32 even with relatively random conductor-wafer positioning.

As mentioned, a single rod conductor may be used. The three-rod conductors described lend themselves to the prior art method of removing the external section since a joint is provided which may be positioned flush with the wafer surface. In a recently designed electron tube, however, it is desirable to use single-rod or integral conductors, preferably of molybdenum, which are hermetically sealed through ceramic wafers. Integral or single piece conductors having multiple or single notched sections may be used in accordance with this in vention since no joint between conductor sections is required as in the prior art. Single rod conductors are less expensive than multiple rod condutcors.

It is also possible to use identical conductors for both the dummy and through conductors. Using one type of conductor simplifies reclaiming the conductors for reuse as described. To permit this simplification, all the conductors of the stem are of the dummy conductor type, but the external portions of some of the conductors are not broken off. The unbroken conductors provide the through conductors. This arrangement is especially feasible in those instances wherein tube bases are used since the external portions of the conductors are soldered and firmly supported within the base pins. In some cases, single notch conductors are preferable due to their greater strength as compared to multiple notched or threaded conductors.

As known, occasionally it is desirable to remove the internal portions of the conductors instead of the external, an apparatus being used to cut off the internal conductor portions. It is found that the apparatus cutters need relatively frequent sharpening. Using notches ment of the cutters with simple knock-out and back-up pins which require considerably less maintenance than in accordance with this invention permits the replacecutters.

What is claimed is: a

1. A stem for an electron tube comprising an insulating wafer having a pair of surfaces, and a plurality of conductors extending through said wafer and outwardly of said surfaces in vacuum tight relation with said wafer, said conductors each comprising a first rod and a second rod butt welded together, the joint between said rods being embedded within said wafer, one of said first rods, and only said first rods, having a length including a number of adjacently disposed cut-out portions, the ends of 5 said length being disposed on opposite sides of one of said surfaces.

2. A stem for an electron tube comprising an insulating wafer having an upper surface and a lower surface, and a plurality of conductors extending through said wafer and outwardly of said surfaces in vacuum tight relation with said wafer, each of said conductors including two rods butt welded together, the joint between said two rods being embedded within said wafer and one of said two rods extending outwardly through said lower surface, all of said one rods, and only said one rods, having a number of adjacently disposed portions of reduced cross-sectional area, some of said port-ions being embedded within said wafer and some of said portions being external thereof,

References Cited by the Examiner UNITED STATES PATENTS 3/38 Cornell.

7/ 43 Mayers 339144 2/50 Greiner 17450.5 X

9/5 3 Carpenter.

2/56 Bychinsky 339-31 X 6/59 Cresswell et a1. 17450.6l 10/61 Pfaender 313-64 FOREIGN PATENTS 6/58 France. 5/25 Great Britain.

15 LARAMIE E. ASKIN, Primary Examiner. 

1. A STEM FOR AN ELECTRON TUBE COMPRISING AN INSULATING WAFER HAVING A PAIR OF SURFACES, AND A PLURALITY OF CONDUCTORS EXTENDING THROUGH SAID WAFER AND OUTWARDLY OF SAID SURFACES IN VACUUM TIGHT RELATION WITH SAID WAFER, SAID CONDUCTORS EACH COMPRISING A FIRST ROD AND A SECOND ROD BUTT WELDED TOGETHER, THE JOINT BETWEEN SAID RODS BEING EMBEDDED WITHIN SAID WAFER, ONE OF SAID FIRST RODS, AND ONLY SAID FIRST RODS, HAVING A LENGTH INCLUDING A NUMBER OF ADJACENTLY DISPOSED CUT-OUT PORTIONS, THE ENDS OF SAID LENGTH BEING DISPOSED ON OPPOSITE SIDES OF ONE OF SAID SURFACES. 